Surface Features

Surface features are characteristics found at or near the polished surface of a
gemstone — technically blemishes rather than inclusions, though the distinction blurs
when a feature extends inward. They carry independent diagnostic information about
authenticity, treatment history, and durability. The most gemmologically significant
are naturals and trigons: a natural is a remnant of the original crystal surface
left by the cutter to preserve weight, confirming natural crystalline origin since
no synthetic material carries a genuine growth surface. Trigons — tiny triangular
growth pits or raised pyramids on diamond octahedron faces — are oriented opposite
to the crystal face and are diagnostic of natural diamond, absent from all synthetic
productions ^[1]. Further down the significance scale, bearding
(fine fractures from bruting), extra facets, laser-drill holes, and surface graining
all provide evidence about cutting history and treatment status. In practical
assessment, reflected-light examination of the girdle at 10–40× is the fastest way
to identify many of these features before committing to immersion or spectroscopy.

Naturals are remnants of the original crystal surface left on a cut gemstone
^[1]:

Characteristics:

• Original rough crystal surface preserved
• Usually found on or near the girdle
• May show trigons (triangular growth marks) ^[1]
• Often left deliberately to preserve weight

Significance:

• Proves natural origin (synthetics don't have naturals) ^[1]
• Acceptable in diamond grading if confined to girdle
• Should not affect face-up appearance

Bearding consists of tiny fractures along the girdle, created during cutting
^[2]:

Formation:

• Created by the bruting (girdling) process
• Mechanical stress causes minute fractures
• Extends from girdle into stone interior

Appearance:

• Hair-like fractures at girdle edge
• Creates "fuzzy" or "fringed" appearance
• Severity ranges from minor to extensive

Grading impact:

• Minor bearding often acceptable
• Heavy bearding can affect clarity grade
• May be reduced by re-polishing girdle

Extra facets are small additional polished surfaces not part of the standard cut:

Purposes:

• Remove surface-reaching inclusions
• Eliminate naturals or damage
• Correct cutting errors

Location:

• Often on pavilion near girdle
• May be on crown
• Should not be visible face-up (ideally)

Grading consideration:

• Generally considered a blemish
• Impact depends on visibility
• Very common in coloured stones

Surface graining appears as visible growth lines on polished surfaces:

Types:

• Whitish graining - Light-coloured lines
• Reflective graining - Shiny, mirror-like lines
• Transparent graining - Subtle lines, often internal origin

Relationship to internal graining:

• Surface graining often continues internally
• Represents structural irregularities
• Related to crystal growth conditions

Etch features result from natural dissolution processes ^[1]:

Etch channels:

• Tube-like cavities extending from surface
• Created by corrosive fluids during geological history
• Often follow crystallographic directions
• Can contain secondary minerals

Etch figures:

• Geometric depressions on crystal faces
• Reflect underlying crystal symmetry
• Trigons on diamond octahedron faces (triangular etch pits) ^[1]
• Hexagonal pits on corundum

Laser drilling is a treatment that creates access channels to internal inclusions:

Purpose:

• Access dark inclusions for bleaching
• Improve apparent clarity

Appearance:

• Very fine, straight channels
• May appear as tiny dots on surface
• Often lead to bleached inclusion sites
• Visible under magnification

Detection:

• Look for unnaturally straight tubes
• Follow tube to inclusion site
• May show surface opening